The bear market definition is exactly the opposite of a bull market. It's a market where quarter after quarter and the market is moving down about 20 percent. Bull Markets and Bear Markets: These terms describe long-term trends, not short -term changes. Bull and bear markets are usually measured in years. As Navin. are bulls and bears. It sounds dangerous but it isn't. You often hear of the market being bullish or bearish. So what is the definition of a bull market and what is.